Abstract
Despite marked improvement in the quality of lives across the globe, more than 2 million individuals in socioeconomically disadvantaged environments remain infected by helminth (worm) parasites. Owing to the longevity of the worms and paucity of immunologic controls, these parasites survive for long periods within the bloodstream, lymphatics, and gastrointestinal tract resulting in pathologic conditions such as anemia, cirrhosis, and lymphatic filariasis. Despite infection, an asymptomatic state may be maintained by the host immunoregulatory environment, which involves multiple levels of regulatory cells and cytokines; a breakdown of this regulation is observed in pathological disease. The role of TLR expression and function in relation to intracellular parasites has been documented but limited studies are available for multicellular helminth parasites. In this review, we discuss the unique and shared host effector mechanisms elicited by systemic helminth parasites and their derived products, including the role of TLRs and sphingolipids. Understanding and exploiting the interactions between these parasites and the host regulatory network are likely to highlight new strategies to control both infectious and immunological diseases.
Highlights
Helminth parasites include an array of metazoan organisms
TLR1, TLR2, TLR4, TLR5, and TLR6 are expressed on the plasma membrane and TLR3, TLR7, TLR8, and TLR9 are present in endosome of leukocytes
Toll-like receptors (TLRs) are key players in the inflammatory process by promoting the production of inflammatory molecules, for example, cytokines and chemokines, and function as regulatory contributors and appear to provide signals that are necessary for the resolution of excessive inflammation
Summary
Helminth parasites (worms) include an array of metazoan organisms. Over 60% of the world populations are at the risk of helminth infections in tropical and subtropical regions [1]. The social and medical impact of the global parasitic worm burden necessitates more attention and research focus on modulation of immune responses to helminth infection and factors that influence disease pathogenesis [5]. Helminth parasites have evolved immune evasion strategies necessary for their continued transmission. This immune evasion is achieved at the expense of both antigen-presenting cells (APCs) and T cells. Similar to intracellular parasitic infections, pattern-recognition receptors (PRR) play a pivotal role in initiating the host immune response against multicellular helminth parasites [6]. Most of the pathogen-associated molecular patterns (PAMPs) from these parasites are recognized by Toll-like receptors (TLRs) [7]. TLRs dictate the downstream pathways involved in adaptive immune responses by influencing multiple antigen-presenting cell (APC) functions [9]. In addition to TLR, NOD (nucleotide oligomerization domain-like receptor) recognizes intracellular PAMPS and initiates signaling pathways that induce production of inflammatory cytokines [11, 12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
